Model for calcite spherulite formation in organic, clay-rich, lacustrine carbonate shales (Barbalha Formation, Aptian, Araripe Basin, NE Brazil)

2021 ◽  
pp. 104988
Author(s):  
H. Claes ◽  
T. Miranda ◽  
T.C. Falcao ◽  
J. Soete ◽  
Z. Mohammadi ◽  
...  
Keyword(s):  
Lacustrine Carbonate ◽  
Organic Clay ◽  
Spherulite Formation

scholarly journals Porosity evolution of high-quality reservoirs in deep Palaeogene lacustrine carbonate rocks in the central Bohai Sea

2018 ◽  
Vol 36 (5) ◽  
pp. 1136-1156 ◽  
Author(s):  
Yuanhua Qing ◽  
Zhengxiang Lü ◽  
Xiandong Wang ◽  
Xiuzhang Song ◽  
Shunli Zhang ◽  
...  
Keyword(s):  
Bohai Sea ◽  
Oil And Gas ◽  
Early Stage ◽  
Reservoir Rock ◽  
Secondary Porosity ◽  
Authigenic Minerals ◽  
Porosity Evolution ◽  
Lacustrine Carbonate ◽  
Reservoir Porosity ◽  
Pore Lining

The oil and gas in the Palaeogene lacustrine carbonate rock reservoirs in the Bohai Sea accumulated during several periods. The reservoir porosity formed during each period affected the degree of accumulation that occurred. In this paper, the percentages of particles, authigenic minerals and pores in the reservoir bed were calculated with the statistical method of microstructure analysis. The formation time was determined with an isotopic analysis of the authigenic carbonate minerals and the homogenization temperature of the gas–liquid inclusions. The percentages of the primary intergranular pores that formed during the different stages were recovered based on the compaction features both before and after the formation of the major authigenic minerals. The evolution of porosity was thus described quantitatively and chronologically, employing the percentages of the residual primary intergranular pores, visceral cavity pores and dissolved pores at the different burial depths. The results indicate that in the initial sediments of the reservoir rock, the primary intergranular porosity was 32.4%. During the early burial stage, the total reservoir porosity increased by up to 46.9%, due to the addition of another type of primary pore, namely visceral cavity pores, which were generated from the decomposition of bioclasts. During the late, deep burial stage, the compaction reduced only 8.2% of the porosity, due to the support of the pore-lining dolomite precipitating during the early stage. Authigenic minerals occupied 12.6% of the porosity, and the dissolution created the secondary porosity by 3.8%. Good preservation of the visceral cavity pores and the growth of the pore-lining dolomites during the early stages are the major factors leading to the high reservoir porosity. The quantitative and chronological characteristics of the reservoir porosity evolution could be described accurately. The prediction of reservoir beds can be better guided than in previously reported methods by applying high resolution microscopic quantitative analysis technology and authigenic mineral timing analysis technology.

Shear Modulus and Damping Ratio for Normally Consolidated Peat and Organic Clay in Hokkaido Area

2018 ◽  
Vol 36 (5) ◽  
pp. 3159-3171 ◽  
Author(s):  
Hirochika Hayashi ◽  
Takahiro Yamanashi ◽  
Hijiri Hashimoto ◽  
Masahiko Yamaki
Keyword(s):  
Shear Modulus ◽  
Damping Ratio ◽  
Organic Clay

scholarly journals Facies and depositional environments for the coquinas of the Morro do Chaves Formation, Sergipe-Alagoas Basin, defined by taphonomic and compositional criteria

2015 ◽  
Vol 45 (3) ◽  
pp. 415-429 ◽  
Author(s):  
Ana Carolina Tavares ◽  
Leonardo Borghi ◽  
Patrick Corbett ◽  
Jane Nobre-Lopes ◽  
Raphael Câmara
Keyword(s):  
Continental Margin ◽  
Carbonate Rocks ◽  
Sedimentary Facies ◽  
High Energy ◽  
Depositional Environments ◽  
Campos Basin ◽  
Lacustrine Carbonate ◽  
Paleoenvironmental Interpretation ◽  
Reservoir Description ◽  
Facies Succession

Lacustrine carbonate rocks form important hydrocarbon accumulations along the Brazilian continental margin, some of which are contained in oil fields in which coquinas are one of the main reservoirs (viz. Campos Basin). The complexity and heterogeneity of these deposits make them a challenge in terms of reservoir description. For the necessary classification and paleoenvironmental interpretation of the coquinas, it is essential to evaluate many aspects including biological (such as carbonate productivity), sedimentological (energy regime in the depositional environment, transport of bioclasts, terrigenous supply), taphonomic (fragmentation of shells, abrasion) and diagenetic processes. The facies analysis applied in this study is considered a more appropriate classification approach to understand these coquinas, since it is more flexible and comprehensive than the existing classifications for carbonate rocks. The material investigated here consists of rock samples of the coquinas from the Atol Quarry of the Morro do Chaves Formation (Barremian/Aptian), Sergipe-Alagoas Basin. These rocks that crop out in the Atol quarry complex can be considered as a case study for similar coquinas reservoirs found in the Brazilian continental margin basins. Six sedimentary facies were described, using the main taphonomic (fragmentation of shells) and compositional (presence of micrite and siliciclastic matrix) features as a diagnostic criteria. Two carbonate facies, two mixed carbonate-siliciclastic facies and two siliciclastic facies (mudstones) were identified. From the facies succession, combined with a review of the literature on the subject, the following depositional paleoenvironments were defined: high-energy lake platform, lacustrine delta in a high-energy lake platform and lake-centre. In this paper, a new facies model for the studied coquinas succession is proposed.

Geoarchaeology of the Midland (Paleoindian) Site, Texas

1996 ◽  
Vol 61 (4) ◽  
pp. 755-771 ◽  
Author(s):  
Vance T. Holliday ◽  
David J. Meltzer
Keyword(s):  
Human Remains ◽  
Radiometric Dating ◽  
High Plains ◽  
Dune Field ◽  
Projectile Points ◽  
Human Bones ◽  
Dating Methods ◽  
Lacustrine Carbonate ◽  
New Type ◽  
Numerical Dating

In 1953 human remains and a new type of Paleoindian artifact were discovered eroding from a "blowout" in a small dune field along Monahans Draw, near Midland, Texas, on the Southern High Plains. The projectile points became the type “Midland” collection. Stratigraphy, radiometric dating, paleontology, and geochemistry suggested that the artifacts and bones dated to at least 10,000 B.P. and that the human remains were possibly as old as 20,000 B.P. The researchers believed that the human bones were from below a red sand that in turn was below a Folsom occupation. The dating of the human remains has long been problematic, however, and recent attempts to apply U-series dating further confuse the story. Geoarchaeological investigations were carried out at the site from 1989 to 1992 to reevaluate the geochronology, with particular reference to the age of the skeletal material. We reach several conclusions: (1) there are two Red Sands; (2) the human remains are from below the upper Red Sand, but the Folsom material is from above the lower Red Sand and, therefore, the Red Sand stratigraphy is not relevant to the age of the human remains; (3) the human remains were associated with the valley-margin facies of a lacustrine carbonate that is well dated in the region and rarely is > 10,000 B.P.; and (4) all numerical dating methods applied at the site produced unreliable results. We find no compelling evidence that the human remains from the Midland site are older than Folsom age; they may be contemporary with or younger than the Folsom occupation.

Comparisons of pyrolysis parameters between source rocks and their clay-sized fractions: Implication for source material of hydrocarbon generation

2022 ◽  
pp. 1-42
Author(s):  
Xiaojun Zhu ◽  
Jingong Cai ◽  
Feng Liu ◽  
Qisheng Zhou ◽  
Yue Zhao ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Material ◽  
Source Rocks ◽  
Natural Environments ◽  
Hydrocarbon Generation ◽  
Petroleum Systems ◽  
Organic Mineral ◽  
Organic Clay ◽  
Organo Clay ◽  
Rock Eval

In natural environments, organic-clay interactions are strong and cause organo-clay composites (a combination between organic matter [OM] and clay minerals) to be one of the predominant forms for OM occurrence, and their interactions greatly influence the hydrocarbon (HC) generation of OM within source rocks. However, despite occurring in nature, dominating the OM occurrence, and having unique HC generation ways, organo-clay composites have rarely been investigated as stand-alone petroleum precursors. To improve this understanding, we have compared the Rock-Eval pyrolysis parameters derived from more than 100 source rocks and their corresponding <2 μm clay-sized fractions (representing organo-clay composites). The results show that all of the Rock-Eval pyrolysis parameters in bulk rocks are closely positively correlated with those in their clay-sized fractions, but in clay-sized fractions the quality of OM for HC generation is poorer, in that the pyrolysable organic carbon levels and hydrogen index values are lower, whereas the residual organic carbon levels are higher than those in bulk rocks. Being integrated with the effects of organic-clay interactions on OM occurrence and HC generation, our results suggest that organo-clay composites are stand-alone petroleum precursors for HC generation occurring in source rocks, even if the source rocks exist in great varieties in their attributes. Our source material for HC generation comprehensively integrates the original OM occurrence and HC generation behavior in natural environments, which differs from kerogen and is much closer to the actual source material of HC generation in source rocks, and it calls for further focus on organic-mineral interactions in studies of petroleum systems.

scholarly journals Past Hydrological Conditions in a Fluvial Valley: Records from C-O Isotope Signatures of Holocene Sediments in the Loire River (France)

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 400
Author(s):  
Philippe Négrel ◽  
Wolfram Kloppmann
Keyword(s):  
Clay Mineralogy ◽  
Local Environment ◽  
Late Glacial ◽  
Alluvial Plain ◽  
River Dynamics ◽  
Basin Scale ◽  
Isotope Record ◽  
Lacustrine Carbonate ◽  
Late Glacial And Holocene ◽  
Loire River

Multi-proxy indices (grainsize distribution, mineralogy, δ18O, δ13C) in sediments from a meander infill in the Middle Loire alluvial plain of central France are used to highlight some aspects of the basin evolution over the period from 0 to 10,000 years BP. During the Late-Glacial and Holocene period, the lacustrine carbonate substratum of the alluvial plain was incised by the Loire River, creating numerous oxbows and channels related to meander migration. The channel fills consist mainly of fine clayey sediments deposited during flooding of the river, with an almost total absence of coarse-clastic and sandy material, except in the basal part. The record of isotope ratio variations together with the distribution of particle sizes allows the evolution of the river dynamics to be constrained. The strong decrease of carbonate δ13C in the upper part of the record is ascribed to a progressive closure of the meander and, thus, an increasing control of the C-isotope signature by biological activity in a local environment. Variations in carbonate δ18O, rather, reflect paleohydrological/paleoclimatic changes at the basin scale. The isotope record of the river dynamics also agrees with the variations in clay mineralogy.

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